1. Field of the Invention
The present invention relates to a method of bonding vulcanized rubber to resin. 2. Description of the Prior Art
Among recently developed various thermoplastic resins, resins called as engineering plastics are known. These resins are polyamide resin, polyester resin, polycarbonate resin, polyacetal resin, polysulfone resin, silicone resin, polyphenylene oxide resin, polyimide resin, ABS resin, methacrylic resin and the like, and many of them are excellent in mechanical strength, heat resistance, creep resistance, chemical resistance, electrical property, dimensional stability and the like, and can be widely used in place of metals, such as iron, zinc, aluminum and the like, under various use conditions.
In general, industrial rubber products are composites composed of rubber and metal; rubber and plastics; and rubber and inorganic substance, but major part of the rubber products are composites composed of rubber and metal. However, in recent industrial rubber products, the rubber-metal composite tends to be replaced by a rubber-resin composite. Industrial rubber composites are now required to have a light weight, excellent corrosion resistance, chemical resistance, wear resistance and electrical property, and a low friction coefficient.
When the composites of rubber and plastics are produced, the rubber must be tightly bonded to the plastics. In the conventional method for bonding rubber to plastics, a chlorine-containing adhesive is applied on the surface of a resin molded article obtained by the extrusion molding and the resin molded article is bonded to an unvulcanized rubber through the adhesive layer by vulcanization. However, this method of bonding resin molded article to rubber through vulcanization has the following drawbacks. That is, the adhesion strength between the resin molded article and the rubber lowers or the resin molded article cracks due to the repeating cooling and heating cycles or to the heat aging during the vulcanization step, and further the adhesion strength varies depending upon the kind of the resin. Moreover, when thermoplastic resins having a low melting point are used among thermoplastic resins, the resin molded article deforms due to the high temperature and pressure during the vulcanization.